The present invention relates to an image reproduction device, comprising an automatic feed unit for documents; a double-sheet detector for detecting more than one sheet as the document for copying; an operator control unit provided with an operator control panel; and a control unit connected to the units for controlling the automatic feed unit, processing the signal from the double-sheet detector and controlling the operator control unit.
The term xe2x80x9cimage reproduction devicexe2x80x9d denotes a digital or analogue copying machine or a document scanner. In a device of this kind, one or more documents for copying are transported, by means of an automatic feed unit, one by one from an input tray to a positioning section where the document is scanned or imaged. In the case of a stack of several documents in the input tray, the documents have to be separated from one another by means of a separating mechanism.
Nevertheless, there are cases in which a plurality of sheets are taken simultaneously from the stack. As a result, it is then not possible to make good copies. Another consequence of this is that problems may occur during transport and there may be the risk that the original documents are damaged. The automatic processing of the documents then has to be interrupted.
To obviate the above disadvantages, a device is known from U.S. Pat. No. 5,383,631 in which a double-sheet detector is disposed within the automatic feed unit. This detector records whether the document being transported comprises a single sheet or a plurality of sheets, e.g. two or three sheets simultaneously. In this way it is possible to detect two originals inadvertently sticking together, thus increasing the reliability of the automatic original processing. If a plurality of sheets are detected, the printing job is interrupted and the originals are returned to the input tray to be fed to the device again. Depending on new double sheet detections, the procedure is repeated a number of times and then the printing job finally stops when the sheets are not successfully separated.
In a device of this kind it is a disadvantage that a so-called paste-up (a sheet on which something has been pasted) as the document for copying will be incorrectly classified as an error input. A document of this kind cannot be copied with the known device without an error message.
The object of the present invention is to provide a reproduction device which is adapted to be operated in a simple manner which is understandable and predictable for the user, and wherein copies of original documents can be made even if the document for copying is formed from more than one sheet.
To this end, according to the present invention, the operator control unit is adapted to offer a choice between switching the double-sheet detector on or off.
In this way, the device according to the present invention is suitable for the image reproduction of documents in cases where, depending on the presence of documents consisting of more than one sheet, the operator is offered the choice of adapting the operation of the image reproduction device thereto.
In one specific embodiment of the device according to the present invention, the operator control unit is adapted to offer, in the case of double-sheet detection, a choice between switching the double-sheet detector off or to leave it on.
In a device of this kind according to the present invention, upon a first double-sheet detection, the operator is offered, by means of a forced dialogue, the choice as to whether or not to switch off the double-sheet detection. If, in a set of documents for copying, a first paste-up is detected by means of the double-sheet detector, the operator is offered the choice of switching the detector off for the rest of the set. In such cases it is probable that there will be more paste-ups in the set. In this way, a set having a plurality of paste-ups can be copied without further interruptions.
If the device according to the present invention is provided with an automatic feed mode, in which the default setting of the double-sheet detector is switched on, the device is suitable for giving the operator, in the case of a first detection of double sheet documents, the option to leave the double-sheet detector switched on for the remaining reproduction process or, in the knowledge of the presence of paste-ups and the like, to continue the procedure without further interruption by opting for switching the detector off.
In a variant of the device according to the present invention, the automatic feed unit is provided with an optional manual feed mode. When this mode is used, the documents can be input to the feed unit one by one manually.
If the device according to the present invention, in one specific embodiment, is provided with an automatic feed unit having a manual feed mode wherein the double-sheet detector default setting is switched off, this has the advantage that the device is suitable for the reproduction of documents consisting of more than one single sheet, without interruption of the print job. The choice of a manual feed mode being offered is of itself sufficient to operate in this mode without problems with respect to double-sheet detection.
It is possible that the manual feed mode may be set by means of a selection menu on the operator control panel of the operator control unit. An alternative suggestion is that this mode may be set by means of a switch connected to the device according to the present invention. The switch can, for example, form part of the automatic feed unit.
The double-sheet detector may be positioned in various locations within the device. For example, it is possible to locate the double-sheet detector at the positioning section for the scanning of the document.
In one embodiment of the device according to the present invention, the automatic feed unit is provided with a separating mechanism and the double-sheet detector is positioned within the automatic feed unit. Preferably, the double-sheet detector is located in the vicinity of the separating mechanism. The effect of this is that the detection of more than one sheet, as the document, during the transport path from the input tray to the positioning section takes place at the beginning of the path and hence at an early time, if the double-sheet detector is placed near the separating mechanism. In this way the risk of transport problems is greatly reduced while at the same time the choice is offered to the operator early on via the operator control panel, to continue or interrupt the reproduction procedure.
The double-sheet detector used in the device according to the present invention may be an ultrasonic transmitter and receiver pair. In this case, the transmitter and receiver are located on either side of the transport path and hence on either side of a document for copying. As the document attenuates the signal transmitted by the transmitter, the signal is recorded by the receiver as an indication of the thickness of the document. From this it is possible to derive whether a single sheet or a plurality of sheets is involved.
The double-sheet detector may consist of a plurality of pairs each comprising a transmitter and receiver. In this way simultaneous detection at different locations is possible. In this way, for example, it is possible to detect whether the document consists of two adhering single sheets of equal size. If the document is a paste-up, in which, for example, just a part of the first sheet is covered by a second sheet, then when a double-sheet detector is used with a plurality of transmitter and receiver pairs such documents differing in form can be detected with respect thereto.